In recent years, a multiband/multisystem advances for radio communication equipment represented by a mobile phone terminal has been made, and a plurality of communication devices are mounted in one terminal. However, the mobile phone terminal itself is continuously required to achieve a reduction in size and thickness, and reduction in size and thickness of a communication device mounted therein is eagerly demanded. Under such a background, a reduction in size and thickness of a component used for the communication device becomes essential, and a reduction in size and thickness of principal parts such as high-frequency filters or duplexers are eagerly desired.
As another method for achieving a reduction in size of the communication device, there is a tendency to simplify the communication device and decrease the number of components used therein. For example, FIG. 12 shows a configuration of a high-frequency block in a conventional mobile phone terminal. In the high-frequency block shown in FIG. 12, a reception path is connected with an inter-stage reception filter 104, and a transmission path is connected with an inter-stage transmission filter 114. On the other hand, a high-frequency block shown in FIG. 13 is configured such that the inter-stage transmission filter and the inter-stage reception filter are omitted for the purpose of simplifying the communication device. The high-frequency block shown in FIG. 12 is provided with an antenna 101, a duplexer 102, a low noise amplifier (LNA) 103, an inter-stage reception filter 104, an LNA 105, mixers 106 and 109, low-pass filters (LPFs) 107 and 110, variable gain amplifiers (VGAs) 108 and 111, a phase control circuit 112, a transmitter 113, an inter-stage transmission filter 114 and a power amplifier (PA) 115. On the other hand, on the high-frequency block shown in FIG. 13, in the reception side, the inter-stage reception filter 104 is omitted, and an LNA 202 is provided to replace the LNAs 103 and 105. Also, on the transmission side, the inter-stage transmission filter 114 is omitted.
In this manner, in the high-frequency block shown in FIG. 13, since the number of the filter elements is reduced, the remaining filter element (duplexer 201) is required to have performances of the two conventional filter elements (inter-stage reception filter 104 and inter-stage transmission filter 114). Specifically, a great enhancement of out-of-band suppression, of the filter characteristic is required. Also, in addition to the above, a great enhancement of isolation between transmission and reception is demanded in the duplexer 201.
In this manner, in the high-frequency filter and duplexer used for a mobile phone terminal and the like, there was a problem that great enhancements in characteristics such as suppression level outside the pass-band and the isolation is required while continuously reducing the size and thickness.
One of the factors that hinder the high suppression and high isolation of the filter and duplexer is unnecessary electromagnetic coupling generated in a substrate on which a filter element is mounted. To solve this problem, for example, in a configuration disclosed in Patent Document 1, a mounted package on which a filter element is mounted disposes a ground pattern (partitioning ground pattern) for partitioning a plurality of wirings present in one wiring layer between the wirings, thereby suppressing unnecessary electromagnetic coupling between the wirings to improve the suppression level of the filter.
Here, for the purpose of suppressing the unnecessary electromagnetic coupling between the wirings, in the case of disposing a ground pattern on the same wiring layer as those wirings, it would be better to make the ground pattern as close as possible to the wirings. This is because electromagnetic fields radiated from the respective wirings will be induced into the partitioning ground pattern for certain, whereby the electromagnetic coupling between the respective wirings will be reduced.    Patent Document 1: JP-A-2006-180192 (Published Application)